High capacity and high efficiency filter deck assembly system and method of use and replacement

ABSTRACT

A rotary drum filter has a plurality of longitudinally extending division grids mounted about the outer circumference of a drum. A plurality of corrugated sheets are provided, with the leading and trailing edges of each sheet mounted to circumferentially adjacent pairs of division grids to define filtrate compartments. An equivalent number of perforated filter plates are also provided. Each filter plate is attached to the top of a corrugated sheet and has a leading edge and a trailing edge that are set back from the leading edge and trailing edge of the corrugated sheet. A seal clip is positioned near the leading edge of each corrugated sheet. A seal member or seal members is/are held in place by the seal clip and is/are positioned at the face of the leading edge of each corrugated sheet or beneath and near the face or each corrugated sheet. A perforated cap strip can be removably attached to the top of each division grid to thereby retain for confined movement each filter plate and corrugated sheet combination (filter deck and drainage deck) during rotary drum filter operation and to allow easy replacement of the filter plate and corrugated sheet combination(s) and/or cap strip(s) when the rotary drum filter is not in operation. This rotary drum filter design and operation has increased capacity and efficiency.

FIELD OF TECHNOLOGY

The present invention relates generally to a filter deck assembly andits method of use and replacement. In particular, the present inventionrelates to a specially designed, constructed, utilized and replaceablehigh capacity and high efficiency filter deck assembly for a rotary drumfilter.

BACKGROUND AND SUMMARY OF TECHNOLOGY

Rotary drum filters are well known and are used in the pulp and paperindustry to filter and wash pulp slurries, for example, from U.S. Pat.Nos. 4,808,265 and 4,906,364 (the entire contents of which are expresslyincorporated hereinto by reference). Rotary drum filters generallycomprise a cylindrical drum mounted for rotation in a tank containing aslurry solution. A filter deck assembly is mounted radially outward ofthe surface of the drum. As the drum is rotated, a low pressure ismaintained inside the drum so that a pulp sheet is formed on the surfaceof the filter deck assembly. The filter deck assembly functions to spacethe pulp from the drum surface to facilitate filtering and drainage.

The filter deck assembly usually includes a filter deck on top and adrainage deck below, which directs the filtrate to filtratecompartments. The liquid filtrate is drawn through the filter deck andthe drainage deck and into the filtrate compartments by a pressuredifferential. Filtrate is removed from the filtrate compartments in aconventional manner. The filter deck assembly must prevent rewetting ofthe pulp sheet as the drum rotates through the descending path of thefiltrate cycle.

Metal plates having fine perforations, slots or other apertures areoften used as the filter deck. Corrugated sheets attached below thefilter decks are used as the drainage decks. The metal plates, thecorrugated sheets, and the drum may each be made of different metals.

The filter deck assembly for rotary drum filters must be capable ofwithstanding differential thermal expansion of the component elementsdue to the temperature variations in the filtering cycles. For example,temperature differentials of up to 100 degrees Fahrenheit expose thefilter deck assembly to heavy thermal shocks once every cylinderrevolution.

Unlike the deck assemblies known to date, the present inventivetechnology provides a filter deck assembly for a rotary drum filter thathas a greater drainage surface, a more efficient filtering action, andis constructed and arranged to permit thermal expansion of the componentelements without resultant damage. Furthermore, the present inventivetechnology provides a filter deck assembly that effectively preventsrewetting of the pulp sheet from a run back of the filtrate as the drumrotates through the descending path of the cycle. The present inventivetechnology also provides a filter deck assembly that is durable and hasa long commercial life. Finally, the present inventive technologyprovides a filter deck assembly that is particularly constructed andarranged to allow simple and quick replacement of filter deck assemblysections.

The foregoing advantages are obtained in a rotary drum filter having aplurality of longitudinally and radially extending division gridsmounted about the outer circumference of a drum. A plurality ofcorrugated sheets for drainage decks are provided, with the leading andtrailing edges of each sheet mounted on circumferentially adjacent pairsof division grids to define filtrate compartments. An equivalent numberof perforated filter decks or plates are also provided. Each filter deckor plate is attached to the top of a corrugated sheet (drainage deck)and has a leading edge that is set back from the leading edge of theattached corrugated sheet. An equivalent number of perforated cap strips(longitudinal cap strips) are attached to the tops of the division gridsto keep the filter deck assemblies within their proper locations andranges of movement, to allow maximum drainage and to allow ease ofreplacement of cap strips and filter deck assemblies.

A seal member is positioned in front of (partially or wholly) and/orunderneath the leading edge, or in close proximity thereto, of eachcorrugated sheet (drainage deck). A seal clip is positioned and attachedin front of and/or underneath the leading edge of each corrugated sheetand holds the seal member in place. The seal clip can be tack-welded orspot welded to the corrugated sheet, for example, and depending on thegeometry, to the front and/or bottom of the corrugated sheet. When theseal member is positioned in front of and/or underneath the corrugatedsheet, the seal member may be configured in a manner so that all or aportion of the seal member is located or pinched between the seal clipand the leading edge, or near the leading edge, of the corrugated sheet.The seal member is a compressible material that acts in conjunction withthe seal clip to, among other things, seal the leading edge area of thedrainage deck when the corresponding portion of the rotary drum isdescending. It also assists with and maximizes the filter deck drainagearea and deck pressure differential in the area of the seal clip.

Some of the problems with the prior art devices are the loss of drainagein the area corresponding to the seal member and the loss of pressuredifferential in that area. For example, the L-shaped seal member of U.S.Pat. No. 4,906,364 results in the loss of drainage in the area of theseal member and the loss of pressure differential in that area. The lossof drainage and pressure differential is detrimental to the capacity ofthe rotary drum filter and degrades washing efficiency. The presentinventive technology provides additional drainage capacity and improvedwashing efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross section of a drum filter according to anembodiment of the present invention.

FIG. 2 is a bottom view of a filter deck assembly according to anembodiment of the present invention.

FIG. 3 is a side view of a filter deck assembly according to anembodiment of the present invention as depicted in FIG. 2.

FIG. 4 is a side view of a filter deck assembly and division gridaccording to an embodiment of the present invention as depicted in FIG.2.

FIG. 5 is a cross sectional view at 5-5 of FIG. 3.

FIG. 6 is a cross sectional view at 6-6 of FIG. 3.

FIG. 7 is a side view of a portion of a drum filter, including filterdeck assemblies, cap strips and division grids according to anembodiment of the present invention as depicted in FIG. 2.

FIG. 8 is a bottom view of a filter deck assembly according to anotherembodiment of the present invention.

FIG. 9 is a side view of a filter deck assembly according to anembodiment of the present invention as depicted in FIG. 8.

FIG. 10 is a side view of a filter deck assembly and division gridaccording to an embodiment of the present invention as depicted in FIG.8.

FIG. 11 is a bottom view of a filter deck assembly according to anotherembodiment of the present invention.

FIG. 12 is a side view of a filter deck assembly according to anembodiment of the present invention as depicted in FIG. 11.

FIG. 13 is a side view of a filter deck assembly and division gridaccording to an embodiment of the present invention as depicted in FIG.11.

FIG. 14 is a cross sectional view at 14-14 of FIG. 12.

FIG. 15 is a side view of a portion of a drum filter, including filterdeck assemblies, cap strips and division grids according to anembodiment of the present invention as depicted in FIG. 11.

FIG. 16 is a bottom view of a filter deck assembly according to anotherembodiment of the present invention.

FIG. 17 is a side view of a filter deck assembly according to anembodiment of the present invention as depicted in FIG. 16.

FIG. 18 is a side view of a filter deck assembly and division gridaccording to an embodiment of the present invention as depicted in FIG.16.

DETAILED DESCRIPTION OF EXEMPLARY ILLUSTRATIVE NON-LIMITING ARRANGEMENTSAND METHODS

The accompanying FIGURES schematically depict filter drums, filter deckassemblies, and configurations of filter deck assemblies, cap strips andgrids that are exemplary, illustrative, non-limiting arrangementsembodying the present inventive technology, including the method of useand replacement.

Referring now to the drawings, wherein similar referenced charactersdesignate corresponding parts throughout the several views, the rotarydrum filtering apparatus illustrated in FIGS. 1 and 2 comprises a drumstructure, generally designated as 70, that is, at the user's place ofbusiness, at least partially submerged in a tank 12 that contains a pulpstock 14 or other slurry to be filtered. The drum is constructed in aconventional manner so that a pressure or vacuum is applied to drainfiltrate and create a pulp sheet 16 on a filter deck assembly 18. Forexample, the pressure differential is created by the filtrate beingatmospheric pressure and the drum being contained in a low pressureenclosure (typically about 3-5 psig). A vacuum assist could be appliedto a filtrate pipe. The filter deck assembly 18 includes a filter deck10 and a drainage deck 20.

As shown in FIG. 1, a plurality of longitudinally extending divisiongrids 90 are mounted on the drum surface 76. The grids are parallel andare spaced evenly about the outer surface of the drum to form filtratecompartments 80 inside the deck assembly. The filter deck assemblies 18and cap strips 100 (longitudinal cap strips) have an appropriatecircumferential radius to form a smooth cylindrical outer deck surfacearound the drum structure.

As can be seen in the preferred embodiments of FIGS. 2-7, the drainagedeck 20 consists of a square or rectangularly shaped corrugated sheet 36having alternating ridges 22 and channels 24. Typical deck assemblydimensions are about ten (10) inches (circumferentially on the drum) byabout seventy-nine (79) inches (longitudinally across the drum) or alength appropriate to ease manufacturing and fit the length of thecylinder. The ridges and channels extend in the direction of drumrotation from a leading edge 25 of the sheet to a trailing edge 26. Thecorrugated sheet 36 is preferably a corrosion resistant metal such asstainless steel or titanium.

Slots, holes or perforations 30 are provided near the trailing edge ofeach channel 24 for communicating filtrate from the drainage deck to thefiltrate compartments. Due to the location of slots, holes orperforations 30 and their operation during the cycle, filtrate flowsfrom the drainage deck 20 into the filtrate compartments 80 during theascending portion of the drum travel. During the descending portion oftravel, the trailing edge location of slots, holes or perforations 30coupled with the leading edge 25 sealing action of sealing member 50 andsealing clip 60 prevents leakage of filtrate from the filtratecompartments 80 which would cause rewetting of the pulp sheet 16.

The filter deck 10 consists of a square or rectangular metal plate 40that is attached to the top of a corresponding corrugated sheet 36. Thefilter plate 40 is perforated with fine holes, slots or apertures 41 andis preferably a corrosion resistant metal such as stainless steel ortitanium. The filter plate 40 is preferably drilled in its entirety withpreferably 1 mm diameter holes on preferably 2 mm centers. The filterplate 40 is preferably attached to some or all of the tops of the ridges22 of the corrugated sheet 36 by suitable welds. Preferably, theattachment spot welds (drilled plate to corrugated sheet) can be in thedrilled holes. The diameter of the spot weld (and quantity of them) cancreate sufficient attachment. The leading edge 42 of the filter plate 40is set back from the leading edge 25 of the attached corrugated sheet36.

Although not critical to the invention, the filter plate 40 does notnecessarily extend past the edges of the corrugated sheet. Instead, anadditional piece of metal (e.g., steel that is or is not perforated likethe filter plate) is welded to the corrugated sheet and fits into acircumferential step (similar to half of a division grid) machined intothe cylinder. Another (circumferential) cap strip overlaps thisadditional piece of metal (e.g., steel) and helps assist with the“floatation” (movement) of the deck assembly. Stated another way, thedeck assembly is not attached on its perimeter. Instead, a “tab” iscreated and attached to the corrugation. This tab is “overlapped” by adifferent (circumferential) cap strip. The nature of this attachment isnot instrumental to the invention and can take the form of conventionaldrum filter machines. On a typical drum filter (over three meters long),there would be three circumferential cap strips, one on each end ringand one on a center ring.

As in typical rotary drum filters, an end ring can be and can look verysimilar to a “one sided” division grid. The step that the seal clip mayrest upon may be on an appropriate radius to meet the radius of the deckplate. The end ring cap strip may be continuous. The division grid capstrip may abut to it. The height may be the same as the division grid. Acenter ring may be similar to a “short” two-sided division grid. It maylook like an inverted “T.” A groove may be machined into the drum forthis ring to mount and steps may be machined into it. It may be “short”(i.e., does not extend to the cylinder wrapper plate) to allow filtrateto flow from one end of the machine to the filtrate discharge end.

In essence, a plane may be established by the cap-strips. This canrestrain the deck from “coming up.” The deck assembly can be supportedby steps around its perimeter. The division grid steps may be on oneplane and the center ring and end ring may be on another. The divisiongrip may support the deck underneath the corrugation. The center and endrings may be supported by clips welded to the underneath of acorrugation “peak” (see FIG. 3 where item 22 points).

In preferred embodiments such as those of FIGS. 2 and 3, the leadingedge 42 and the trailing edge 44 of the filter plate 40 do not extendbeyond the leading edge 25 and the trailing edge 26 of the corrugatedsheet 36. In further preferred embodiments, the leading edge 42 is setback so that the resulting gap 68 is slightly larger than (or at mostequal to) the resulting gap 66. In other words, when in descendingoperation, the seal clip 60 on the corrugated sheet 36 can contact thedivision grid 90, which then prevents filter plate 40 from contactingthe cap strip 100 (or, when the gaps are equal, prevent filter plate 40from contacting cap strip 100 forcefully). This advantageously extendsthe life of the filter plate 40 and cap strip 100, and it furtherimproves their combined and increased filtering capacity withoutaffecting the integrity of the filter deck panel assembly.

In preferred embodiments such as FIGS. 2-7, a sealing member 50 ispositioned near the underneath leading edge 25 of each corrugated sheet36 and is engaged between a sealing clip 60 and the modified leadingedge 25 of corrugated sheet 36 as shown in FIG. 3. The sealing member 50is a compliant material and preferably abuts the corrugated sheet 36 soas to close any gap between the sealing clip 60 and the corrugated sheet36. The sealing member 50 and sealing clip 60 prevent filtrate in thefiltrate compartment 80 from leaking back into the channels of thedrainage deck 20 and rewetting the pulp sheet 16.

The sealing clip 60 is preferably solid sheet material, and it ispreferably the same material as used for the corresponding corrugatedsheet, which avoids deleterious component interaction and temperaturechange problems. The sealing clip 60 is preferably welded to the leadingedge 25 of the corrugated sheet 36. The thickness of the sealing clip 60can be between about 0.5 and about 4.0 millimeters.

The sealing member 50 is preferably engaged between the sealing clip 60and the corrugated sheet 36 by the clamping action of the sealing clip60 or a conventional means of engaging. For example, the seal clip 60may contain the seal member 50 by clamping it in position prior to thewelding of the seal clip 60 to the leading edge of the corrugated sheet36 or portions thereof. Teflon, EPDM (ethylene-propylene rubber), Viton,Gore-Tex and/or another compressible material, or combination ofmaterial that acts in a compressible fashion, are suitable materials forthe sealing member 50. The sealing member 50 can be relatively thin, forexample, between about 1.0 and about 4.0 millimeters in thickness. Thesealing member 50 can extend beyond the bottommost portion of thecorrugated sheet 36.

In other preferred embodiments such as those of FIGS. 8-10, a secondsealing member 50 b, or continuous sealing member 50 a and 50 b (i.e.,wherein sealing members 50 a and 50 b are one continuous sealing memberand are not separate members as shown in FIG. 9), is positioned near theface of leading edge 25 of each corrugated sheet 36 and is engagedbetween a sealing clip 60 and the modified leading edge of corrugatedsheet 36 as shown in FIG. 9. The sealing members 50 a and 50 b (or onecontinuous sealing member) are a compliant material and substantiallyabut the leading and underneath edges of corrugated sheet 36 so as toeffectively close any gap between the sealing members 50 a and 50 b andthe leading edge of corrugated sheet 36. The sealing clip 60 clamps thesealing members and is welded to the corrugated sheet. The lower portionof sealing member 50 a (like the lower portions of sealing members 50 inFIGS. 3 and 17) can extend beyond the bottommost portion of corrugatedsheet 36. The nature of the sealing member (50 a in FIG. 9, 50 in FIGS.3 and 17) is to seal between sealing clip 60 and grid 90. Sealing member50 b can provide (if necessary) additional leakage protection.

The sealing members 50 a and 50 b (or one continuous sealing member) andsealing clip 60 prevent filtrate in the filtrate compartment 80 fromleaking back into the channels of the drainage deck 20 and rewetting thepulp sheet 16 during descent. In addition, when the rotary drum filteris in operation, the assembly may slide forward toward the division grid90 (for example, as originally set up, as develops over time duringoperation of the rotary drum filter, or when a filter deck panelassembly is on a descending path) such that the sealing members 50 a and50 b (or one continuous sealing member) and the sealing clip 60 can besubstantially pinched between the leading edge 25 of the corrugatedsheet 36 and the division grid 90 and thereby further prevent filtratein the filtrate compartment 80 from leaking back into the channels ofthe drainage deck 20 and rewetting the pulp sheet 16.

In the preferred embodiments such as those of FIGS. 8-10, the sealingclip 60 is preferably solid sheet material, and it is preferably thesame material as used for the corresponding corrugated sheet 36, whichavoids deleterious component interaction and temperature changeproblems. The sealing clip 60 is preferably welded to a portion of theleading edge 25 of the corrugated sheet 36. It can be welded at the topleading edge of the corrugated sheet or other portions, and must becapable of substantially holding the sealing members 50 a and 50 b (orone continuous sealing member) in place, e.g., to ensure that thesealing members 50 a and 50 b (or one continuous sealing member) are/issubstantially held in position when the rotary drum filter is inoperation. The thickness of the sealing clip 60 can be between about 0.5and about 4.0 millimeters.

In the preferred embodiments such as those of FIGS. 8-10, the sealingmembers 50 a and 50 b (or one continuous sealing member) are/ispreferably engaged between the sealing clip 60 and the corrugated sheet36 by the clamping action of the sealing clip 60 or a conventional meansof engaging. For example, the “J” shaped seal clip 60 may contain thesealing members 50 a and 50 b (or one continuous sealing member) byclamping them/it in position prior to the welding of the seal clip 60 tothe top leading edge of the corrugated sheet 36 or portions thereof.Teflon, EPDM (ethylene-propylene rubber), Viton, Gore-Tex and/or anothercompressible material, or combination of material that acts in acompressible fashion, are suitable materials for the sealing members 50a and 50 b (or one continuous sealing member). The sealing members 50 aand 50 b (or one continuous sealing member) can be relatively thin, forexample, between about 1.0 and about 4.0 millimeters in thickness.

In other preferred embodiments such as those of FIGS. 11-15, a sealingmember 50 is positioned near the face of leading edge 25 of eachcorrugated sheet 36 and is engaged between a sealing clip 60 and themodified leading edge of corrugated sheet 36 as shown in FIG. 12. Thesealing member 50 is a compliant material and substantially abuts theleading edge of corrugated sheet 36 so as to effectively close any gapbetween the sealing member 50 and the leading edge of corrugated sheet36. The sealing clip 60 clamps the sealing member and is welded to thecorrugated sheet.

The sealing member 50 and sealing clip 60 prevent filtrate in thefiltrate compartment 80 from leaking back into the channels of thedrainage deck 20 and rewetting the pulp sheet 16 during descent. Inaddition, when the rotary drum filter is in operation, the assembly mayslide forward toward the division grid 90 (for example, when a filterdeck panel assembly is on a descending path) such that the sealingmember 50 and the sealing clip 60 can be substantially pinched betweenthe leading edge 25 of the corrugated sheet 36 and the division grid 90and thereby further prevent filtrate in the filtrate compartment 80 fromleaking back into the channels of the drainage deck 20 and rewetting thepulp sheet 16.

In the preferred embodiments such as those of FIGS. 11-15, the sealingclip 60 is preferably solid sheet material, and it is preferably thesame material as used for the corresponding corrugated sheet 36, whichavoids deleterious component interaction and temperature changeproblems. The sealing clip 60 is preferably welded to a bottom (orunderneath) portion of the leading edge 25 of the corrugated sheet 36,and must be capable of substantially holding the sealing member 50 inplace, e.g., to ensure that the sealing member 50 is substantially heldin position when the rotary drum filter is in operation. The thicknessof the sealing clip 60 can be between about 0.5 and about 4.0millimeters.

In the preferred embodiments such as those of FIGS. 11-15, the sealingmember 50 is preferably engaged between the sealing clip 60 and thecorrugated sheet 36 by the clamping action of the sealing clip 60 or aconventional means of engaging. For example, the elongated “J” shapedseal clip 60 may contain the sealing member 50 by clamping it inposition prior to the welding of the seal clip 60 to the bottom (orunderneath) leading edge of the corrugated sheet 36 or portions thereof.Teflon, EPDM (ethylene-propylene rubber), Viton, Gore-Tex and/or anothercompressible material, or combination of material that acts in acompressible fashion, are suitable materials for the sealing member 50.The sealing member 50 can be relatively thin, for example, between about1.0 and about 4.0 millimeters in thickness.

In other embodiments such as those of FIGS. 16-18, a sealing member 50is positioned near the lower face of leading edge 25 of each corrugatedsheet 36 and is engaged between a sealing clip 60 and the unmodifiedleading edge of corrugated sheet 36 as shown in FIG. 17. The sealingmember 50 is a compliant material and abuts the lower leading edge ofcorrugated sheet 36. The sealing clip 60 clamps the sealing member andis welded to the corrugated sheet. The lower portion of sealing member50 (like the lower portions of sealing member 50 in FIG. 3 and 50 a inFIG. 9) can extend beyond the bottommost portion of corrugated sheet 36.The nature of the sealing member (50 a in FIG. 9, 50 in FIGS. 3 and 17)is to seal between sealing clip 60 and grid 90.

The sealing member 50 and sealing clip 60 prevent filtrate in thefiltrate compartment 80 from leaking back into the channels of thedrainage deck 20 and rewetting the pulp sheet 16 during descent. Inaddition, when the rotary drum filter is in operation, the assembly mayslide forward toward the division grid 90 (for example, as originallyset up, as develops over time during operation of the rotary drumfilter, or when a filter deck panel assembly is on a descending path)such that the sealing member 50 and the sealing clip 60 can besubstantially pinched between the leading edge 25 of the corrugatedsheet 36 and the division grid 90 and thereby further prevent filtratein the filtrate compartment 80 from leaking back into the channels ofthe drainage deck 20 and rewetting the pulp sheet 16.

In the embodiments such as those of FIGS. 16-18, the sealing clip 60 ispreferably solid sheet material, and it is preferably the same materialas used for the corresponding corrugated sheet 36, which avoidsdeleterious component interaction and temperature change problems. Thesealing clip 60 is preferably welded to a portion of the leading edge 25of the corrugated sheet 36, and must be capable of substantially holdingthe sealing member 50 in place, e.g., to ensure that the sealing member50 is substantially held in position when the rotary drum filter is inoperation. The thickness of the sealing clip 60 can be between about 0.5and about 4.0 millimeters.

In the embodiments such as those of FIGS. 16-18, the sealing member 50is preferably engaged between the sealing clip 60 and the corrugatedsheet 36 by the clamping action of the sealing clip 60 or a conventionalmeans of engaging. For example, a “U” shaped seal clip 60 may containthe sealing member 50 by clamping it in position prior to the welding ofthe seal clip 60 to the leading edge of the corrugated sheet 36 orportions thereof. Teflon, EPDM (ethylene-propylene rubber), Viton,Gore-Tex and/or another compressible material, or combination ofmaterial that acts in a compressible fashion, are suitable materials forthe sealing member 50. The sealing member 50 can be relatively thin, forexample, between about 1.0 and about 4.0 millimeters in thickness.

As seen in FIGS. 1, 4, 7, 10, 13, 15 and 18, the longitudinallyextending division grids 90 are provided with two shoulder portions 92and 94, one on each longitudinal face of the grid. The shoulders areadapted to support the leading edge 25 portion of one corrugated sheet36 and the trailing edge 26 portion of a circumferentially adjacentcorrugated sheet. The shoulders on each grid can be of equal lengths ordiffering lengths in either direction, as desired, so long as theysupport the corrugated sheets and allow proper movement. The gap 66between the grid 90 and the drain deck 20 allows for thermal expansion.Additionally, the gap 68 between the filter deck 10 and cap strip 100allows for thermal expansion.

An embodiment of the invention includes a cap strip 100 to provide afree floating deck assembly as shown in FIGS. 1, 4, 7, 10, 13, 15 and18. In this embodiment, the leading edge of the filter plate 40 is setback from the leading edge 25 of the corrugated sheet 36, and thetrailing edge 44 of the filter plate 40 is set back from the trailingedge 26 of the corrugated sheet 36. The size of gap 68 must be greaterthan or equal to gap 66; otherwise, the cap strip 100 may shear off.

Preferably, the longitudinally extending cap strip 100 is attached tothe division grid 90 to overlap the leading and trailing edges of theadjacent corrugated sheets 36. Only the cap strip 100 may be attached,preferably by suitable welds, to the division grid 90. The cap strips100 have fine perforations, slots or other apertures as shown in theFIGURES (and like the fine perforations, slots or other apertures in thefilter plates 40 as described and shown in the FIGURES). However, unlikethe perforated filter plates 40, it is preferred that the cap strips arenot drilled/perforated in the area of the welding to the division grids.The design of the subject invention, including the cap strips havingfine perforations, slots or other apertures, provide a filter deckassembly system having high capacity and high efficiency.

The deck assemblies 18 may be considered free floating and may becontained only by the cap strips 100. A replaceable cap strip 100 can beremoved to free (e.g., replace) a deck assembly without damaging thedeck assembly.

Each of the embodiments of the present inventive technology minimizespotential tolerance constraints on the circumferential stackup in themanufacture and assembly of the deck sections. The embodiments allowspace for thermal expansion of both the filter plates and corrugatedsheets. The deck assemblies of the embodiments can expand withoutbreaking welds or bending parts.

While the inventive technology has been described in connection withwhat are presently considered to be the most practical and preferredembodiments, it is to be understood that the invention is not to belimited to the disclosed embodiments, but on the contrary, is intendedto cover various modifications and equivalent arrangements includedwithin the spirit and scope of the appended claims.

1. A rotary drum filter comprising: (a) a drum mounted for rotation, (b)a plurality of longitudinally extending division grids mounted andspaced in parallel relationship about the outer circumferential surfaceof the drum, (c) a plurality of corrugated sheets each sheet havingalternating ridges and channels extending from a leading edge to atrailing edge, the leading and trailing edges of each sheet mounted onadjacent pairs of division grids to define filtrate compartments aroundthe circumference of the drum, (d) drainage slots near the trailing edgeof each channel for communication to said compartments, (e) a pluralityof perforated filter plates, each filter plate attached to the top of acorresponding corrugated sheet, (f) a seal clip disposed at a leadingedge of each corrugated sheet, (g) a seal member disposed close to theunderside leading edge of each corrugated sheet and engaged between theseal clip and the corrugated sheet, and (h) shoulder portions on bothlongitudinal faces of each division grid adapted to slidably andreplaceably mount respective leading and trailing edges ofcircumferentially adjacent corrugated sheets.
 2. The rotary drum filteraccording to claim 1, wherein the sealing member comprises Teflon,ethylene-propylene rubber, Viton, Gore-Tex and/or another compressiblematerial.
 3. The rotary drum filter according to claim 1, wherein theseal clip and corrugated sheet are made from a material comprising acommon material, austenitic stainless steels or combinations thereof. 4.The rotary drum filter according to claim 1, wherein the seal clip is astraight shape, J shape, reverse L shape or other shape that securelyanchors the seal member.
 5. The rotary drum filter according to claim 1,wherein each perforated filter plate has a leading edge that is set backfrom the leading edge of the corresponding corrugated sheet.
 6. Therotary drum filter according to claim 5, wherein each perforated filterplate has a trailing edge that is set back from the trailing edge ofsaid corrugated sheet.
 7. The rotary drum filter according to claim 6further comprising longitudinally extending cap strips that areremovably fixed to the division grids so as to overlap the leading andtrailing edges of the adjacent corrugated sheets.
 8. The rotary drumfilter according to claim 7, wherein the cap strips are perforated.
 9. Afilter deck assembly comprising: (a) a corrugated sheet havingalternating ridges and channels extending from a leading edge to atrailing edge, and having drainage slots near the trailing edge of eachchannel, (b) a perforated filter plate attached to the top of thecorrugated sheet, (c) a seal clip disposed at a leading edge of thecorrugated sheet, and (d) a seal member disposed close to the undersideleading edge of each corrugated sheet and engaged between the seal clipand the corrugated sheet.
 10. The filter deck assembly according toclaim 9, wherein the seal member comprises Teflon, ethylene-propylenerubber, Viton, Gore-Tex and/or another compressible material.
 11. Thefilter deck assembly according to claim 9, wherein the seal clip andcorrugated sheet are made from a material comprising a common material,austenitic stainless steels or combinations thereof.
 12. The filter deckassembly according to claim 9, wherein each perforated filter plate hasa leading edge that is set back from the leading edge of thecorresponding corrugated sheet.
 13. The filter deck assembly accordingto claim 12, wherein each perforated filter plate has a trailing edgethat is set back from the trailing edge of said corrugated sheet. 14.The filter deck assembly according to claim 13 further comprising atleast one longitudinally extending cap strip that can be removably fixedto a division grid in a rotary drum filter so as to overlap the leadingand trailing edges of the adjacent corrugated sheets.
 15. The filterdeck assembly according to claim 14, wherein the cap strip isperforated.
 16. A method of filtering or washing pulp slurriescomprising: (a) placing a pulp slurry in a tank with a rotary drumfilter, (b) using the rotary drum filter to filter or wash the pulpslurry, wherein the rotary drum filter has at least one filter deckassembly comprising: (1) a corrugated sheet having alternating ridgesand channels extending from a leading edge to a trailing edge, andhaving drainage slots near the trailing edge of each channel, (2) aperforated filter plate attached to the top of the corrugated sheet, (3)a seal clip disposed at a leading edge of the corrugated sheet, and (4)a seal member disposed close to the underside leading edge of eachcorrugated sheet and engaged between the seal clip and the corrugatedsheet.
 17. The method of filtering or washing pulp slurries according toclaim 16, wherein the filter deck assembly further comprises at leastone longitudinally extending cap strip that can be removably fixed to adivision grid in the rotary drum filter so as to overlap a leading edgeand a trailing edge of the corrugated sheet.
 18. The method of filteringor washing pulp slurries according to claim 17, wherein the cap strip isperforated.
 19. A method of replacing a filter deck assembly comprising:(a) removing a spent or broken filter deck assembly, and (b) replacingthe spent or broken filter deck assembly with a new filter deck assemblycomprising: (1) a corrugated sheet having alternating ridges andchannels extending from a leading edge to a trailing edge, and havingdrainage slots near the trailing edge of each channel, (2) a perforatedfilter plate attached to the top of the corrugated sheet, (3) a sealclip disposed at a leading edge of the corrugated sheet, and (4) a sealmember disposed close to the underside leading edge of each corrugatedsheet and engaged between the seal clip and the corrugated sheet. 20.The method of replacing a filter deck assembly according to claim 19further comprising the use of perforated cap strips to retain the newfilter deck assembly in the rotary drum filter.
 21. A rotary drum filtercomprising: (a) a drum mounted for rotation, (b) a plurality oflongitudinally extending division grids mounted and spaced in parallelrelationship about the outer circumferential surface of the drum, (c) aplurality of corrugated sheets each sheet having alternating ridges andchannels extending from a leading edge to a trailing edge, the leadingand trailing edges of each sheet mounted on adjacent pairs of divisiongrids to define filtrate compartments around the circumference of thedrum, (d) drainage slots near the trailing edge of each channel forcommunication to said compartments, (e) a plurality of perforated filterplates, each filter plate attached to the top of a correspondingcorrugated sheet, (f) a seal clip disposed under and in front of aleading edge of each corrugated sheet, (g) a seal member disposed underand/or in front of the leading edge of the corrugated sheet and held inplace by the seal clip, and (h) shoulder portions on both longitudinalfaces of each division grid adapted to slidably and replaceably mountrespective leading and trailing edges of circumferentially adjacentcorrugated sheets.
 22. The rotary drum filter according to claim 21,wherein the sealing member comprises Teflon, ethylene-propylene rubber,Viton, Gore-Tex and/or another compressible material.
 23. The rotarydrum filter according to claim 21, wherein the seal clip and corrugatedsheet are made from a material comprising a common material, austeniticstainless steels or combinations thereof.
 24. The rotary drum filteraccording to claim 21, wherein the seal clip is a J shape, elongated Jshape, reverse L shape, elongated reverse L shape, or other shape thatsecurely anchors the seal member.
 25. The rotary drum filter accordingto claim 21, wherein each perforated filter plate has a leading edgethat is set back from the leading edge of the corresponding corrugatedsheet.
 26. The rotary drum filter according to claim 25, wherein eachperforated filter plate has a trailing edge that is set back from thetrailing edge of said corrugated sheet.
 27. The rotary drum filteraccording to claim 26 further comprising longitudinally extending capstrips that are removably fixed to the division grids so as to overlapthe leading and trailing edges of the adjacent corrugated sheets. 28.The rotary drum filter according to claim 27, wherein the cap strips areperforated.
 29. The rotary drum filter according to claim 21, whereinthe seal member has a first piece and a second piece and wherein thefirst piece is under the leading edge of the corrugated sheet and thesecond piece is in front of the leading edge of the corrugated sheet.30. A filter deck assembly comprising: a) a corrugated sheet havingalternating ridges and channels extending from a leading edge to atrailing edge, and having drainage slots near the trailing edge of eachchannel, b) a perforated filter plate attached to the top of thecorrugated sheet, c) a seal clip disposed under and in front of aleading edge of each corrugated sheet, and d) a seal member disposedunder and/or in front of the leading edge of the corrugated sheet andheld in place by the seal clip.
 31. The filter deck assembly accordingto claim 30, wherein the seal member comprises Teflon,ethylene-propylene rubber, Viton, Gore-Tex and/or another compressiblematerial.
 32. The filter deck assembly according to claim 30, whereinthe seal clip and corrugated sheet are made from a material comprising acommon material, austenitic stainless steels or combinations thereof.33. The filter deck assembly according to claim 30, wherein eachperforated filter plate has a leading edge that is set back from theleading edge of the corresponding corrugated sheet.
 34. The filter deckassembly according to claim 33, wherein each perforated filter plate hasa trailing edge that is set back from the trailing edge of saidcorrugated sheet.
 35. The filter deck assembly according to claim 34further comprising at least one longitudinally extending cap strip thatcan be removably fixed to a division grid in a rotary drum filter so asto overlap the leading and trailing edges of the adjacent corrugatedsheets.
 36. The filter deck assembly according to claim 35, wherein thecap strip is perforated.
 37. The filter deck assembly according to claim30, wherein the seal member has a first piece and a second piece andwherein the first piece is under the leading edge of the corrugatedsheet and the second piece is in front of the leading edge of thecorrugated sheet.
 38. A method of filtering or washing pulp slurriescomprising: (a) placing a pulp slurry in a tank with a rotary drumfilter, (b) using the rotary drum filter to filter or wash the pulpslurry, wherein the rotary drum filter has at least one filter deckassembly comprising: (1) a corrugated sheet having alternating ridgesand channels extending from a leading edge to a trailing edge, andhaving drainage slots near the trailing edge of each channel, (2) aperforated filter plate attached to the top of the corrugated sheet, (3)a seal clip disposed under and in front of a leading edge of eachcorrugated sheet, and (4) a seal member disposed under and/or in frontof the leading edge of the corrugated sheet and held in place by theseal clip.
 39. The method of filtering or washing pulp slurriesaccording to claim 38, wherein the filter deck assembly furthercomprises at least one longitudinally extending cap strip that can beremovably fixed to a division grid in the rotary drum filter so as tooverlap a leading edge and a trailing edge of the corrugated sheet. 40.The method of filtering or washing pulp slurries according to claim 39,wherein the cap strip is perforated.
 41. A method of replacing a filterdeck assembly comprising: (a) removing a spent or broken filter deckassembly, and (b) replacing the spent or broken filter deck assemblywith a new filter deck assembly comprising: (1) a corrugated sheethaving alternating ridges and channels extending from a leading edge toa trailing edge, and having drainage slots near the trailing edge ofeach channel, (2) a perforated filter plate attached to the top of thecorrugated sheet, (3) a seal clip disposed under and in front of aleading edge of each corrugated sheet, and (4) a seal member disposedunder and/or in front of the leading edge of the corrugated sheet andheld in place by the seal clip.
 42. The method of replacing a filterdeck assembly according to claim 41 further comprising the use ofperforated cap strips to retain the new filter deck assembly in therotary drum filter.
 43. A filter deck assembly comprising: a) acorrugated sheet having alternating ridges and channels extending from aleading edge to a trailing edge, and having drainage slots near thetrailing edge of each channel, b) a perforated filter plate attached tothe top of the corrugated sheet, c) a seal clip disposed solely in frontof a leading edge of each corrugated sheet, and d) a seal memberdisposed in front of the leading edge of the corrugated sheet and heldin place by the seal clip.
 44. The filter deck assembly according toclaim 43, wherein the seal member comprises Teflon, ethylene-propylenerubber, Viton, Gore-Tex and/or another compressible material.
 45. Thefilter deck assembly according to claim 43, wherein the seal clip andcorrugated sheet are made from a material comprising a common material,austenitic stainless steels or combinations thereof.
 46. The filter deckassembly according to claim 43, wherein each perforated filter plate hasa leading edge that is set back from the leading edge of thecorresponding corrugated sheet.
 47. The filter deck assembly accordingto claim 43, wherein each perforated filter plate has a trailing edgethat is set back from the trailing edge of said corrugated sheet. 48.The filter deck assembly according to claim 47 further comprising atleast one longitudinally extending cap strip that can be removably fixedto a division grid in a rotary drum filter so as to overlap the leadingand trailing edges of the adjacent corrugated sheets.
 49. The filterdeck assembly according to claim 48, wherein the cap strip isperforated.
 50. A method of filtering or washing pulp slurriescomprising: (c) placing a pulp slurry in a tank with a rotary drumfilter, (d) using the rotary drum filter to filter or wash the pulpslurry, wherein the rotary drum filter has at least one filter deckassembly comprising: (1) a corrugated sheet having alternating ridgesand channels extending from a leading edge to a trailing edge, andhaving drainage slots near the trailing edge of each channel, (2) aperforated filter plate attached to the top of the corrugated sheet, (3)a seal clip disposed solely in front of a leading edge of eachcorrugated sheet, and (4) a seal member disposed in front of the leadingedge of the corrugated sheet and held in place by the seal clip.
 51. Themethod of filtering or washing pulp slurries according to claim 50,wherein the filter deck assembly further comprises at least onelongitudinally extending cap strip that can be removably fixed to adivision grid in the rotary drum filter so as to overlap a leading edgeand a trailing edge of the corrugated sheet.
 52. The method of filteringor washing pulp slurries according to claim 51, wherein the cap strip isperforated.
 53. A method of replacing a filter deck assembly comprising:(c) removing a spent or broken filter deck assembly, and (d) replacingthe spent or broken filter deck assembly with a new filter deck assemblycomprising: (1) a corrugated sheet having alternating ridges andchannels extending from a leading edge to a trailing edge, and havingdrainage slots near the trailing edge of each channel, (2) a perforatedfilter plate attached to the top of the corrugated sheet, (3) a sealclip disposed solely in front of a leading edge of each corrugatedsheet, and (4) a seal member disposed in front of the leading edge ofthe corrugated sheet and held in place by the seal clip.
 54. The methodof replacing a filter deck assembly according to claim 53 furthercomprising the use of perforated cap strips to retain the new filterdeck assembly in the rotary drum filter.